Back light system for minimizing non-display area of liquid crystal display device

ABSTRACT

A liquid crystal display device having a liquid crystal display element, a backlight for supplying light to the liquid crystal display element and a case for accommodating the liquid crystal display element and the backlight. The backlight has a light guide plate and a lamp unit, wherein the lamp unit providing a fluorescent tube, bushings made of an insulating material, a lamp reflector and a lamp cable and the lamp reflector holds the fluorescent tube through the bushings, and made by bending a stiff metal plates.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 09/030,083, filedFeb. 25, 1998, now U.S. Pat. No. 6,147,724, the subject matter of whichis incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to a liquid crystal display device andmore particularly to a liquid crystal display device with a reducedpicture-frame area around the display area that does not contribute tothe display.

To meet the growing demands for acquiring necessary information andperforming computation anytime and anywhere, portable informationprocessing devices as shown in FIG. 52 have been developed. The portableinformation processing devices include notebook type personal computers(hereinafter referred to as a notebook computer), word processors, aportable information terminal, and a pocket type computer.

These portable information processing devices mostly use a liquidcrystal display device due to its small thickness, lightness, and smallpower consumption.

The liquid crystal display device comprises a liquid crystal displaypanel for displaying an image and a drive circuit. The drive circuit isprovided around the liquid crystal display panel and constitutes anon-display area (so-called picture-frame area) that does not contributeto the display.

There have been growing demands in recent years for increasing thedisplay area in the portable information processing devices so that thedisplay can be viewed easily. A simple way of increasing the displayarea is to use a large liquid crystal display device, but this degradesthe portability, the very feature of the portable information processingdevices.

Hence, certain picture-frame reduction techniques have been employed toreduce the non-display are and thereby increase the display area ascompared with that of liquid crystal display devices with the sameexternal size.

Such picture-frame reduction techniques are disclosed in Japanese PatentApplication No. 75019/1994 and 297234/1995 and have been successful tosome extent.

The inventors of this invention, however, have found that problems stillremain to be solved in making the display area larger and thepicture-frame area smaller than those of the conventional devices.

FIG. 53A shows a case ML of the liquid crystal display device mountedwith a backlight comprising a light guide plate GLB and a fluorescenttube LP. FIG. 53B is a cross section taken along the line B—B of FIG.53A. FIG. 53C is a cross section taken along the line C—C of FIG. 53A.

The conventional liquid crystal display devices, as shown in FIG. 53Band FIG. 53C, use lamp cables LPC1, LPC2 with round cross sections forsupplying a voltage to the fluorescent tube LP.

Hence, the area where the lamp cables LPC1, LPC2 are installed in theliquid crystal display device becomes large, making it impossible toreduce the picture-frame area of the liquid crystal display device.

SUMMARY OF THE INVENTION

An object of this invention is to reduce the picture-frame area notcontributing to the display on the liquid crystal display device.

To achieve the above object, the liquid crystal display device of thepresent invention comprises a liquid crystal display element, abacklight to provide light to the liquid crystal display element, and acase accommodating the liquid crystal display element and the backlight,wherein a lamp cable for supplying a voltage to the backlight is formedas a flat cable made of a conductive foil and an insulating filmlaminated together and is arranged between the backlight and the liquidcrystal display element.

The liquid crystal display device of the present invention ischaracterized in that the device comprises a liquid crystal displayelement, a backlight to provide light to the liquid crystal displayelement, and a case accommodating the liquid crystal display element andthe backlight, wherein a lamp cable for supplying a voltage to thebacklight is formed of a flat cable made of a conductive foil and aninsulating film laminated together, the backlight has a light emittingfluorescent tube and insulating bushings covering electrodes at the endsof the fluorescent tube, the lamp cable is connected to one of theelectrodes of the fluorescent tube and is bent along the surface of thefluorescent tube, and the bushing covers that part of the lamp cablewhich is bent along the surface of the fluorescent tube.

The liquid crystal display device of the present invention ischaracterized in that the device comprises a liquid crystal displayelement, a backlight to provide light to the liquid crystal displayelement, and a case accommodating the liquid crystal display element andthe backlight, wherein a lamp cable for supplying a voltage to thebacklight is formed of a flat cable made of a conductive foil and aninsulating film laminated together, the lamp cable has a terminalconnected to an electrode of the fluorescent tube, the terminal of thelamp cable is connected to one of the electrodes of the fluorescent tubeby soldering and the solder is exposed from the terminal of the lampcable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an end view of a lamp unit, a light source of the liquidcrystal display device;

FIG. 1B is a cross section of the part of the lamp unit where thefluorescent tube LP and the lamp cable LPC3 are connected;

FIG. 1C is a cross section taken along the line I—I of FIG. 1A;

FIG. 2A is a top plan view of a liquid crystal display module MDL asviewed from the top (i.e., upper side or display side) of the liquidcrystal display element PNL;

FIG. 2B is a left side view of the liquid crystal display module MDL;

FIG. 2C is a right side view of the liquid crystal display module MDL;

FIG. 2D is a front side view of the liquid crystal display module MDL;

FIG. 2E is a rear side view of the liquid crystal display module MDL;

FIG. 3 is a bottom view of the liquid crystal display module MDL of thisinvention, i.e. a bottom view of the liquid crystal display element;

FIG. 4A is a cross section of the liquid crystal display module MDLtaken along the line I—I of FIG. 2A;

FIG. 4B is a cross section of the liquid crystal display module MDLtaken along the line II—II of FIG. 2A;

FIG. 5A is a cross section of the liquid crystal display module MDLtaken along the line III—III of FIG. 2A;

FIG. 5B is a cross section of the liquid crystal display module MDLtaken along the line IV—IV of FIG. 2A;

FIG. 6A is an enlarged view of part A of FIG. 2A;

FIG. 6B is an enlarged view of part B of FIG. 2A;

FIG. 6C is an enlarged view of part C of FIG. 2B;

FIG. 7A is a top plan view of an upper shield case SHD;

FIG. 7B is a right side view of the upper shield case SHD;

FIG. 7C is a left side view of the upper shield case SHD;

FIG. 7D is a rear side view of the upper shield case SHD;

FIG. 7E is a front side view of the upper shield case SHD;

FIG. 8A is a top plan view of a mold case ML;

FIG. 8B is a left side view of the mold case ML;

FIG. 8C is a right side view of the mold case ML;

FIG. 8D is a front side view of the mold case ML;

FIG. 8E is a rear side view of the mold case ML;

FIG. 9 is a bottom view of the mold case ML;

FIG. 10A is a cross section of the mold case ML taken along the line I—Iof FIG. 8A;

FIG. 10B is a cross section of the mold case ML taken along the lineIII—III of FIG. 8D;

FIG. 10C is a cross section of the mold case ML taken along the lineII—II of FIG. 8A;

FIG. 10D is a cross section of the mold case ML taken along the lineIV—IV of FIG. 8A;

FIG. 10E is a cross section of the mold case ML taken along the line V—Vof FIG. 8A;

FIG. 10F is a cross section of the mold case ML taken along the lineVI—VI of FIG. 8A;

FIG. 10G is a cross section of the mold case ML taken along the lineVII—VII of FIG. 9;

FIG. 11A is a top plan view of a frame spacer WSPC;

FIG. 11B is a left side view of the frame spacer WSPC;

FIG. 11C is a right side view of the frame spacer WSPC;

FIG. 11D is a front side view of the frame spacer WSPC;

FIG. 11E is a rear side view of the frame spacer WSPC;

FIG. 12 is a bottom view of the frame spacer WSPC;

FIG. 13A is a cross section of the frame spacer WSPC taken along theline I—I of FIG. 11D;

FIG. 13B is a cross section of the frame spacer WSPC taken along theline II—II of FIG. 11D;

FIG. 13C is a cross section of the frame spacer WSPC taken along theline III—III of FIG. 11C;

FIG. 13D is a cross section of the frame spacer WSPC taken along theline IV—IV of FIG. 11C;

FIG. 13E is a cross section of the frame spacer WSPC taken along theline V—V of FIG. 11A;

FIG. 13F is a cross section of the frame spacer WSPC taken along theline VI—VI of FIG. 11A;

FIG. 14A is a top plan view of a first lower shield case LF1;

FIG. 14B is a left side view of the first lower shield case LF1;

FIG. 14C is a right side view of the first lower shield case LF1;

FIG. 14D is a front side view of the first lower shield case LF1;

FIG. 15A is a top plan view of a second lower shield case LF2;

FIG. 15B is a left side view of the second lower shield case LF2;

FIG. 15C is a right side view of the second lower shield case LF2;

FIG. 15D is a front side view of the second lower shield case LF2;

FIG. 15E is a rear side view of the second lower shield case LF2;

FIG. 15F is an enlarged view of part I enclosed by a dashed line of FIG.15A;

FIG. 15G is a cross section taken along the line II—II of FIG. 15F;

FIG. 15H is a cross section taken along the line III—III of FIG. 15E;

FIG. 15I is a cross section taken along the line IV—IV of FIG. 15A;

FIG. 16A is a plan view of a first prism sheet PRS1;

FIG. 16B is a side view of the first prism sheet PRS1 as viewed from thedirection of the arrow of FIG. 16A;

FIG. 17A is a plan view of a second prism sheet PRS2;

FIG. 17B is a side view of the second prism sheet PRS2 as viewed fromthe direction of the arrow of FIG. 17A;

FIG. 18 is a plan view of a polarized light reflection plate POR;

FIG. 19A is a plan view of a fluorescent tube LP;

FIG. 19B is a side view of the fluorescent tube LP;

FIG. 19C is a cross section taken along the line I—I of FIG. 19A;

FIG. 20A is a plan view of a lamp cable LPC3;

FIG. 20B is a cross section taken along the line I—I of FIG. 20A;

FIG. 20C is an enlarged view of part II of FIG. 20B;

FIG. 21A is a plan view of a first rubber bushing GB1;

FIG. 21B is a view of the first rubber bushing GB1 as viewed fromdirection 1 of FIG. 21A;

FIG. 21C is a view of the first rubber bushing GB1 as viewed fromdirection 2 of FIG. 21A;

FIG. 21D is a cross section taken along the line I—I of FIG. 21B;

FIG. 21E is a cross section taken along the line II—II of FIG. 21B;

FIG. 22A is a plan view of a second rubber bushing GB2;

FIG. 22B is a view of the second rubber bushing GB2 as viewed fromdirection 1 of FIG. 22A;

FIG. 22C is a view of the second rubber bushing GB2 as viewed fromdirection 2 of FIG. 22A;

FIG. 23A is a plan view of a lamp reflector LS;

FIG. 23B is a view of the lamp reflector LS as viewed from direction 1of FIG. 23A;

FIG. 24A is a cross section of the lamp reflector LS taken along theline I—I of FIG. 23A;

FIG. 24B is a cross section of the lamp reflector LS taken along theline II—II of FIG. 23A;

FIG. 24C is a cross section of the lamp reflector LS taken along theline III—III of FIG. 23A;

FIG. 25A is a plan view of an O-ring OL;

FIG. 25B is a cross section of the O-ring OL taken along the line I—I ofFIG. 25A;

FIG. 26A is a plan view of a unit of a combination of a light guideplate GLB, a reflection sheet RFS and a diffusion sheet SPS, as viewedfrom the diffusion sheet SPS side;

FIG. 26B is a side view of a unit of a combination of the light guideplate GLB, the reflection sheet RFS and the diffusion sheet SPS;

FIG. 27A is a plan view of the light guide plate GLB;

FIG. 27B is a side view of the light guide plate GLB as viewed fromdirection 1 of FIG. 27A;

FIG. 28A is a plan view of the reflection sheet RFS;

FIG. 28B is a side view of the reflection sheet RFS as viewed fromdirection 1 of FIG. 28A;

FIG. 29A is a plan view of the diffusion sheet SPS;

FIG. 29B is a side view of the diffusion sheet SPS as viewed fromdirection 1 of FIG. 29A;

FIG. 29C is an enlarged view of part I of FIG. 29B;

FIG. 29D is an enlarged view of part II of FIG. 29A;

FIG. 30A is a plan view of a liquid crystal display element PNL mountedat its outer periphery with a scan signal line-side flexible printedcircuit board FPC1 and with a video signal line-side flexible printedcircuit board FPC2 before being bent;

FIG. 30B is a plan view showing an interface printed circuit board PCB;

FIG. 31A is a plan view of the scan signal line-side flexible printedcircuit board FPC1;

FIG. 31B is an enlarged plan view of part I of the scan signal line-sideflexible printed circuit board FPC1 that is connected to the terminal ofthe liquid crystal display element PNL;

FIG. 32 is a plan view of the video signal line-side flexible printedcircuit board FPC2;

FIG. 33 is a plan view of the interface printed circuit board PCB;

FIG. 34 is an enlarged perspective view of a part where the liquidcrystal display element PNL is connected with the FPC1 and the FPC2;

FIG. 35 is a cross section taken along the line I—I of FIG. 34;

FIG. 36 is a block diagram showing an equivalent circuit of the liquidcrystal display module MDL;

FIG. 37A illustrates the flow of display data between a host computerand a controller unit 101 of an embodiment;

FIG. 37B illustrates the flow of display data between the host computerand the controller unit 101 of another embodiment;

FIG. 38 illustrates the relation of supply of electricity to the liquidcrystal display module MDL;

FIG. 39 illustrates the arrangement of an EMI filter on the interfaceprinted circuit board PCB;

FIG. 40 is a plan view of a pixel portion of the liquid crystal displayelement PNL;

FIG. 41 is a cross section taken along the line I—I of FIG. 40;

FIG. 42 is a cross section taken along the line II—II of FIG. 40;

FIG. 43 is a cross section taken along the line III—III of FIG. 40;

FIG. 44 illustrates drive signal waveforms of a TFT liquid crystaldisplay element TFT-LCD;

FIG. 45A is a bottom view of a liquid crystal display module of a secondembodiment of this invention;

FIG. 45B is a side view of the liquid crystal display module of a secondembodiment of this invention;

FIG. 46A illustrates a liquid crystal display device broken by adestructive test;

FIG. 46B illustrates a part where the light guide plate GLB abutsagainst the glass substrate SUB1 during the destructive test;

FIGS. 47A, 47B and 47C are cross sections of the liquid crystal displaymodule MDL of a third embodiment of this invention provided with ameasure for preventing the glass substrate of the liquid crystal displayelement PNL from being broken by strong impacts;

FIG. 48A is a plan view of the light guide plate GLB of a fourthembodiment of this invention;

FIG. 48B is an enlarged view of a projection PJ5 of FIG. 48A;

FIG. 49A illustrates an example where a chip IC1 on the liquid crystaldisplay element PNL is attached to the shield case SHD with adouble-sided adhesive tape BAT;

FIG. 49B illustrates an example where the liquid crystal display elementPNL is secured to the shield case SHD by sticking a double-sidedadhesive tape BAT on a portion where the liquid crystal display elementPNL and the video signal line-side flexible printed circuit board FPC2overlap;

FIGS. 49C and 49D illustrate an example where a vinyl chloride spacerCLSPC is installed between the IC chips;

FIG. 49E illustrates an example where rubber spacers GSPC are installedbetween the IC chips to protect the IC chips;

FIG. 49F illustrates an example where the vinyl chloride spacers CLSPCare installed between the IC chips and at a portion where the liquidcrystal display element PNL and the flexible printed circuit board FPC2overlap;

FIGS. 50A and 50B are cross sections of a sixth embodiment of thisinvention in which the glass substrates SUB1, SUB2 of the liquid crystaldisplay element PNL are secured to the shield case SHD;

FIGS. 51A and 51B are cross sections of another example of the sixthembodiment of this invention in which the glass substrates SUB1, SUB2 ofthe liquid crystal display element PNL are secured to the shield caseSHD;

FIG. 52 illustrates the liquid crystal display device of this inventionmounted on an information processing apparatus;

FIGS. 53A, 53B and 53C illustrate a structure for housing a backlight,of a conventional liquid crystal display device; and

FIG. 54 illustrates an example for comparison to explain the advantagesof this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, this invention will be described in conjunction with variouspreferred embodiments.

Embodiment 1

The major parts of the first embodiment of this invention are shown inFIGS. 1A, 1B and 1C.

FIG. 1A shows an external view of a lamp unit, the light source of theliquid crystal display device (hereinafter referred to as a liquidcrystal display module MDL).

FIG. 1B is a cross section of a part of the lamp unit where thefluorescent tube LP and the lamp cable LPC3 are connected.

FIG. 1C is a cross section taken along the line I—I of FIG. 1A.

According to this invention because the lamp cable LPC3 is formed as aflat cable, as shown in FIG. 1B, it can be installed in a narrow spacebetween the liquid crystal display element and the backlight, so thatthe picture-frame area of the liquid crystal display module MDL can bereduced.

Further, according to this invention, as shown in FIG. 1B, because thelamp cable LPC3 is formed as a flat cable and bent along the surface ofthe fluorescent tube LP, and because both the fluorescent tube LP andthe lamp cable LPC3 are covered with a rubber bushing GB1, it ispossible to reduce the size of the portion that holds the fluorescenttube LP and therefore the picture-frame area of the liquid crystaldisplay module MDL.

Further, as shown in FIG. 1B, the lamp cable LPC3 is led out of the lampreflector LS and the rubber bushing GB1 through openings (or slits)HOPS, HOPG of the lamp reflector LS and the rubber bushing GB1.According to this invention because the rubber bushing GB1 is exposedfrom the end of the opening HOPS, the lamp cable LPC3 is protectedagainst damage by pointed metal parts or burrs formed when making thelamp reflector LS by blanking.

As shown in FIG. 1B, the lamp cable LPC3 inside the rubber bushing GB1is bent at a portion where a metal foil is sandwiched between insulatingfilms, and thus the lamp cable LPC3 is prevented from being broken inthe rubber bushing GB1.

According to this invention, as shown in FIG. 1C, the terminal TRM ofthe lamp cable LPC3 is made narrower than the region of the fluorescenttube LP where solder LPSOL is provided.

FIG. 54 represents a comparative example for comparison with thisinvention. In the example of FIG. 54, the terminal TRM2 of the lampcable LPC3 completely covers the region of the fluorescent tube LPprovided with the solder LPSOL to increase the connection area betweenthe terminal TRM2 and the terminal of the fluorescent tube LP. Hence,with the comparative example of FIG. 54, the state of the connectionbetween the terminal TRM2 and the electrode of the fluorescent tube LPcannot be checked, leaving a possibility that the lamp of the liquidcrystal display device may fail to turn on due to defective connectionof the lamp cable LPC3.

According to this invention because the solder LPSOL is exposed from theterminal TRM2, as shown in FIG. 1C, the state of connection between thefluorescent tube LP and the lamp cable LPC3 can be checked, eliminatingthe possibility of turn-on failure of the lamp of the liquid crystaldisplay device.

The construction of the liquid crystal display module MDL to which thisinvention is applied will be described in detail.

<<Appearance of Liquid Crystal Display Module MDL>>

FIGS. 2A, 2B, 2C, 2D and 2E are complete assembly drawings of the liquidcrystal display module MDL. FIG. 2A is a front view as viewed from thefront (i.e., upper side or display side) of the liquid crystal displayelement PNL. FIG. 2D is a front side view, FIG. 2C is a right side view,FIG. 2B is a left side view, and FIG. 2E is a rear side view.

FIG. 3 is a complete assembly drawing of the liquid crystal displaymodule MDL, as viewed from the bottom (lower side) of the liquid crystaldisplay element.

The module MDL has two kinds of housing and holding member, a mold caseML and a shield case SHD.

HLD1, HLD2, HLD3 and HLD4 are four mounting holes to mount the moduleMDL as a display unit on an information processing apparatus, such asnotebook type personal computers and word processors.

The shield case SHD of FIG. 7 is formed with mounting holes HLD1, HLD2,HLD3 and HLD4 at locations aligned with the mounting holes HLD1, HLD2,HLD3 and HLD4 of the mold case ML of FIG. 8. Screws or other fasteningsare inserted into these mounting holes to secure the mold case ML andthe shield case SHD to the information processing apparatus. In thismodule MDL, an inverter IV for the backlight is installed in a recessbetween the mounting holes HLD1 and HLD3, as shown in FIG. 52, to supplyelectricity to the fluorescent tube LP of the backlight through theconnector LCT and the lamp cables LPC1, LPC2. Signals from the hostcomputer and necessary electricity are supplied through an interfaceconnector CT1 provided at the back of the module to the controller unitand power supply unit of the liquid crystal display module MDL.

The liquid crystal display module MDL shown in FIG. 2 has the followingdimensions: the long side W (the side defined by the corners on the HLD1and HLD2 sides) is 297.5 mm, the short side H (the side defined by thecorners on the HLD2 and HLD4 sides) is 214.5 mm, the thickness T is 8.0mm, the width X1 measured from the display area AR (the effective pixelarea) to the upper edge of the shield case SHD (on the line II—II ofFIG. 2) is 3.9 mm, the width X2 to the lower edge (on the line I—I ofFIG. 2) is 7.9 mm, the width Y1 to the left edge (on the line III—III ofFIG. 2) is 15.5 mm, and the width Y2 to the right edge (on the lineIV—IV of FIG. 2) is 4.2 mm.

The display area AR has a 270.3 mm long side W and a 202.8 mm short sideand has a diagonal length of 34 cm (13.3 inches).

In the display area AR are arranged 1024 pixels along the long side(horizontal or x direction) and 768 pixels along the short side(vertical or y direction), one pixel consisting of three R, G, B colorpixels.

The liquid crystal display module MDL of FIG. 2 has an advantage overthe liquid crystal display module MDL described in the Japanese PatentApplication No. 297234/1995 mentioned earlier in that, although theexternal dimensions and the display area AR of the liquid crystaldisplay module MDL are large, the picture-frame area not contributing tothe display is small. Hence, with the liquid crystal display module MDLshown in FIG. 2, an easy-to-view large display can be obtained withoutdegrading the portability of the portable information processingapparatuses. The liquid crystal display module MDL of FIG. 2 weighsabout 650 g, light enough for use in portable information processingapparatuses.

The mounting holes of the liquid crystal display module MDL are shapedas shown in FIGS. 6A and 6B. The mounting holes on the lamp cables LPC1,LPC2 side (see part B in FIG. 2A) have a round shape like HLD3 shown inFIG. 6B. The mounting holes on the interface connector CT1 (see part Ain FIG. 2A) side are formed into a U-shaped notch like HLD2 of FIG. 6A.

The arrangement (see part C) of pins of the interface connector CT1 forconnection with an external device (e.g., host computer) of the liquidcrystal display module MDL is shown in FIG. 6C.

<<Cross Section of Liquid Crystal Display Module MDL>>

FIG. 4A is a cross section of the liquid crystal display module MDLtaken along the line I—I of FIG. 2. FIG. 4B is a cross section of theliquid crystal display module MDL taken along the line II—II of FIG. 2.FIG. 5A is a cross section of the liquid crystal display module MDLtaken along the line III—III of FIG. 2. FIG. 5B is a cross section ofthe liquid crystal display module MDL taken along the line IV—IV of FIG.2.

Members shown in FIGS. 4A and 4B and FIGS. 5A and 5B will be describedbelow.

Symbol SHD denotes a shield case (upper case) that covers the peripheryof the liquid crystal display element PNL and the drive circuit of theliquid crystal display element PNL.

Symbol ML denotes a mold case (lower case) to accommodate the backlight.

LF1 and LF2 denote first and second lower shield cases covering thelower case.

WSPC denotes a frame spacer surrounding the backlight.

SUB1 and SUB2 denote glass substrates constituting the liquid crystaldisplay element PNL. In this embodiment, SUB1 is a substrate on whichare formed thin-film transistors and pixel electrodes, and SUB2 is asubstrate on which color filters and common electrodes are formed.

FUS denotes a sealing material that seals liquid crystals in betweenSUB1 and SUB2.

BM denotes a light shielding film formed on the SUB2. In the liquidcrystal display module MDL of this embodiment, the area surrounding thedisplay area AR that is shielded from light by the light shielding filmBM is optimized, so that even when the user views the display area at anangle of more than 45 degrees, neither light directly leaking from thebacklight nor the area around the display area AR not related to thedisplay (for example, an area hidden by the frame spacer WSPC) areviewed. Hence, there is no need to cover the glass substrates SUB1, SUB2with the shield case more than necessary, allowing the picture-framearea to be reduced.

POL1 denotes an upper polarizing plate bonded to the glass substrateSUB2, and POL2 is a lower polarizing plate bonded to the glass substrateSUB1. The liquid crystal display element PNL of this embodiment displaysan image by transmitting or interrupting the light emitted from thebacklight by means of the polarizing plates POL1, POL2 and the liquidcrystal layer interposed between the glass substrates SUB1 and SUB2.

VINC1 denotes a viewing angle enlarging film bonded to the glasssubstrate SUB2, and VINC2 is a viewing angle enlarging film bonded tothe glass substrate SUB1. In this embodiment, the glass substrates SUB1,SUB2 are thus provided with the viewing angle enlarging films toeliminate the viewing angle dependence wherein the contrast varies withthe angle at which the user views the display-a problem inherent in theliquid crystal display element. In the liquid crystal display module MDLof this embodiment, therefore, the viewing angle enlarging filmeliminate a contrast difference between the central part and theperipheral part of the display area AR, realizing a liquid crystaldisplay device having a wide display area with a diagonal size D of 34cm (13.3 inches) or larger.

Although the viewing angle enlarging films may be bonded to the outsideof the polarizing plates, they are provided between the polarizingplates and the glass substrates in this embodiment to enhance theviewing angle enlargement effect.

Symbol LP denotes a fluorescent tube, the light source of the backlight.

GLB denotes a light guide plate of the backlight that turns the lightcoming from the fluorescent tube LP into a uniform plane light sourcedirected toward the glass substrates SUB1, SUB2. The light guide plateGLB is tapered in cross section so that it is thick on the fluorescenttube LP side and thin on the opposite side to reduce its weight.

RFS denotes a reflection sheet that reflects the light reaching thebottom of the light guide plate GLB toward the light guide plate GLB.

SPS denotes a diffusion sheet that diffuses in various directions thelight emitted from the upper surface of the light guide plate GLB towardthe liquid crystal display element PNL.

PRS denotes a prism sheet PRS that converges the light diffused by thediffusion sheet SPS into a predetermined range of output angle toenhance the luminance of the backlight.

POR denotes a polarizing reflection plate which is provided to improvethe luminance of the liquid crystal display device. The polarizingreflection plate POR transmits only light having a specific polarizingaxis and reflects light with other polarizing axes. Thus, by aligningthe polarizing axis of light transmitted by the polarizing reflectionplate POR with the polarizing axis of the lower polarizing plate POL2,the light, which has been absorbed by a conventional lower polarizingplate POL2, can be changed, after traveling back and forth between thepolarizing reflection plate POR and the light guide plate GLB, intopolarized light that passes through the lower polarizing plate POL2 andcan be outputted from the polarizing reflection plate POR, increasingthe luminance of the liquid crystal display device.

LS denotes a lamp reflector that reflects light emitted from thefluorescent tube LP toward the light guide plate GLB. The lamp reflectorLS also holds the fluorescent tube LP as described later. Because thelamp reflector LS holds the light guide plate GLB from both sides andthus is secured to the light guide plate GLB as shown in FIG. 4A, thefluorescent tube LP can be replaced easily.

The frame spacer WSPC mentioned earlier holds the peripheral part of thelight guide plate GLB and the hook of the frame spacer WSPC is insertedinto the hole of the mold case ML to firmly secure the light guide plateGLB to the mold case ML, thus preventing the light guide plate GLB frombutting against the liquid crystal display element PNL. In thisembodiment, the diffusion sheet SPS, the prism sheet PRS and thepolarizing reflection plate POR are also held by the frame spacer WSPC,so that the diffusion sheet SPS, the prism sheet PRS and the polarizingreflection plate POR do not distort, allowing the backlight thatilluminates the liquid crystal display element PNL with a diagonal sizeD of 34 cm (13.3 inches) or larger to be installed in the liquid crystaldisplay device.

The frame spacer WSPC has a function of precisely aligning thepolarizing axis of the transmitted light through the polarizingreflection plate POR with the polarizing axis of the liquid crystaldisplay element PNL (more precisely, the polarizing axis on thebacklight side defined by the lower polarizing plate POL2 or theorientation film of the glass substrate SUB2).

That is, as shown in FIG. 5A, because the frame spacer WSPC holdsimmovably one side of the polarizing reflection plate POR by onesidewall of the frame spacer WSPC, the polarizing axes of the polarizingreflection plate POR and the liquid crystal display element PNL areprevented from becoming deviated due to the rotational movement.

Further, in this embodiment, because the polarizing reflection plate PORand the liquid crystal display element PNL are held by the same holdingmember, or the frame spacer WSPC, the polarizing axes of the polarizingreflection plate POR and the liquid crystal display element PNL are notdeviated even when a strong impact is exerted on the liquid crystaldisplay module MDL.

Prevention of deviation of the polarizing axes of the liquid crystaldisplay element PNL and the polarizing reflection plate POR is animportant factor. If these polarizing axes become misaligned, theluminance of the liquid crystal display module MDL greatly deteriorates,rendering the image display impossible in the worst case.

Symbol GC1 denotes a rubber cushion installed between the frame spacerWSPC and the glass substrate SUB1.

LPC3 denotes a lamp cable for supplying voltage to the fluorescent tubeLP, is formed which cable as a flat cable to reduce the installationspace. This cable is installed between the frame spacer WSPC and thelamp reflector LS. The lamp cable LPC3 is bonded to the lamp reflectorLS with double-sided adhesive tape, so that when the fluorescent tube LPis replaced, the lamp cable LPC3 can be replaced together with the lampreflector LS, eliminating the need to detach the lamp cable LPC3 fromthe fluorescent tube LP and facilitating the replacement of thefluorescent tube LP. Further, the lamp cable LPC3 is made of amultilayer film of flexible films and metal films and thus serves as acushion to prevent interference between the frame spacer WSPC and thelamp reflector LS.

OL denotes an O-ring serving as a cushion between the fluorescent tubeLP and the lamp reflector LS. The O-ring OL is made of a transparentplastic so as not to lower the luminance. The O-ring OL is also made ofan insulating material with a low dielectric constant. Further, theO-ring OL also serves as a cushion to prevent the fluorescent tube LPfrom butting against the light guide plate GLB.

IC1 denotes a drain driver chip for driving the video signal line of theliquid crystal display element PNL. It has a drive circuit integrated ina semiconductor chip mounted on the glass substrate SUB1. The draindriver chip IC1 is mounted on only one of the four sides of the glasssubstrate SUB1, so that on the side opposite the side where the draindriver chip IC1 is mounted, the picture-frame area of the liquid crystaldisplay module MDL can be reduced (see FIG. 1B). The fluorescent tube LPand the lamp reflector LS are stacked below the part of the glasssubstrate SUB1 where the drain driver chip IC1 is mounted. Thisarrangement allows the fluorescent tube LP and the lamp reflector LS tobe installed compactly in the liquid crystal display module MDL.

IC2 denotes a gate driver chip for driving the scan signal line of theliquid crystal display element PNL. It has a drive circuit integrated ina semiconductor chip mounted on the glass substrate SUB1.

Although the mounting technique of this embodiment has been described asan example of an active-matrix liquid crystal display device usingthin-film transistors, it can also be applied to a passive-matrix liquidcrystal display device with no thin-film transistors. In the case of apassive-matrix liquid crystal display device, as the drain driver chipIC1, a segment driver chip is used and is mounted on the glass substrateSUB1, and as the gate driver chip IC2, a common driver chip is used andis mounted on the glass substrate SUB2.

FPC1 denotes a scan signal line-side flexible printed circuit boardwhich is connected to external terminals of the glass substrate SUB1through an anisotropic conductive film to supply electricity and drivesignals to the gate driver chip IC2. On the scan signal line-sideflexible printed circuit board FPC1 are mounted such chip parts EP asresistors and capacitors.

FPC2 denotes a video signal line-side flexible printed circuit boardwhich is connected to external terminal of the glass substrate SUB1through an anisotropic conductive film to supply electricity and drivesignals to the drain driver chip IC1. On the video signal line-sideflexible printed circuit board FPC2 are mounted such chip parts EP asresistors and capacitors. In this embodiment, to reduce thepicture-frame area, the video signal line-side flexible printed circuitboard FPC2 is bent to wrap the lamp reflector LS, with a part b of theFPC2 securely held between the mold case ML at the back of the backlightand the second lower shield case LF2. The mold case ML is provided withnotches to secure a space for the chip parts EP. The video signalline-side flexible printed circuit board FPC2 comprises a thin part athat can easily be bent and a thick part b for multilayer wiring. Inthis embodiment, because the lower shield case that covers the bottomsurface of the liquid crystal display module MDL is divided into a firstlower shield case LF1 and a second lower shield case LF2, the lampreflector LS can be exposed by removing the second lower shield case LF2and turning over the video signal line-side flexible printed circuitboard FPC2, facilitating the replacement of the fluorescent tube LP.

PCB denotes an interface printed circuit board formed with a powersupply circuit and a controller circuit and is made of a multilayerprinted circuit board. In this embodiment, to reduce the picture-framearea, the interface printed circuit board PCB is stacked under the scansignal line-side flexible printed circuit board FPC1 and bonded to theglass substrate SUB1 with a double-sided adhesive tape BAT.

As shown in FIG. 5A, the interface printed circuit board PCB is providedwith a connector CTR4 connected to a connector CT4 of the video signalline-side flexible printed circuit board FPC2. Though not shown, theFPC1 is also electrically connected through a connector to the PCB.

Symbol SUP denotes a reinforcement plate installed between the firstlower shield case LF1 and the connector CT4 to prevent the connector CT4from coming off the connector CTR4.

SPC4 denotes a spacer made of non-woven cloth, which is installedbetween the shield case SHD and the upper polarizing plate POL1 and isbonded to the shield case with an adhesive material. The spacer SPC4 maybe replaced with a double-sided adhesive tape to bond SHD and POL1together.

In this embodiment, to prevent the liquid crystal display element PNLfrom projecting from the shield case SHD, the upper polarizing platePOL1 of plastic film is extended from the glass substrate SUB1 and heldby the shield case SHD as shown in FIG. 4B. With this arrangement inwhich the upper polarizing plate POL1 projecting from the glasssubstrate SUB2 is held by the shield case SHD, this embodiment has asufficient strength even when the picture-frame area is reduced.

Prevention of the liquid crystal display element PNL from projectingfrom the shield case SHD can also be realized by extending the viewingangle enlarging film VINC1 of plastic film from the glass substrate SUB1and holding the extended VINC1 with the shield case SHD. In thisembodiment, both the upper polarizing plate POL1 and the viewing angleenlarging film VINC1 are extended from the glass substrate SUB1 and heldby the shield case SHD, so that even if the area where the shield caseSHD covers the liquid crystal display element PNL is small, the liquidcrystal display element PNL does not project from the shield case SHD.

Symbol DSPC denotes a drain spacer installed between the shield case SHDand the glass substrate SUB1 to prevent the shield case SHD and theglass substrate SUB1 from butting against each other. The drain spacerDSPC covers the drain driver chip IC1 and has a notch NOT at a locationcorresponding to the drain driver chip IC1, so that the SHD and DSPC donot butt against the drain driver chip IC1, which is therefore protectedagainst breakage. The drain spacer DSPC also holds the video signalline-side flexible printed circuit board FPC2 on the external connectionterminals of the glass substrate SUB1 to prevent it from being separatedfrom the glass substrate SUB1, thus ensuring reliable electricalconnection between the SUB1 and the FPC2. The drain spacer DSPC is madeof vinyl chloride plastic that does not collapse when an impact isexerted to protect the drain driver chip IC1 and which can absorb an impact to some extent to protect the glass substrate SUB1.

FUS denotes a sealing material FUS applied in the liquid crystalinjection port.

BAT denotes a double-sided adhesive tape. In this embodiment, as shownin FIGS. 5A and 5B, on the gate driver chip IC2 side (G side) and on theliquid crystal filling port side of the liquid crystal display elementPNL, the glass substrate SUB2 on the color filter side is bonded to theshield case SHD with the double-sided adhesive tape BAT. As shown inFIG. 4B, on the side (LD side) of the liquid crystal display element PNLwhere the drain driver chip IC1 is not mounted, the glass substrate SUB2is bonded to the shield case SHD through the spacer SPC4 to which anadhesive is applied (The spacer SPC4 performs a function equivalent to adouble-sided adhesive tape.) Hence, in this embodiment, except for theside (D side) of the liquid crystal display element PNL where the draindriver chip IC1 is mounted, the liquid crystal display element PNL isbonded to the shield case SHD and not displaced from the shield case SHDif it receives a strong impact.

Further, in this embodiment, on the liquid crystal filling port side theends of the glass substrate SUB1 and the glass substrate SUB2 aresubstantially aligned and bonded as shown in FIG. 5B. Because the endportion where the glass substrate SUB1 and the glass substrate SUB2 arestacked in alignment with each other is held between the shield case SHDand the frame spacer WSPC to fix the liquid crystal display element PNL,the area where the shield case SHD covers the liquid crystal displayelement PNL can be reduced and the portion of the glass substrate SUB1or glass substrate SUB2 held between the shield case SHD and the framespacer WSPC does not crack even if it receives a strong impact. Further,the end portions where the glass substrates SUB1 and SUB2 are stackedmay be held between the shield case SHD and the mold case ML to fix theliquid crystal display element PNL. The construction, in which the endportions where the glass substrates SUB1 and SUB2 are stacked are heldbetween the shield case SHD and the frame spacer WSPC to fixedly supportthe liquid crystal display element PNL, can also be applied to the LDside (see FIG. 4B). This means that, by adopting the construction inwhich the end portions where the glass substrates SUB1 and SUB2 arestacked are supported on both the LD side and the liquid crystal fillingport side, the picture-frame area can be reduced further and the liquidcrystal display module MDL can withstand stronger impacts.

Next, members making up the liquid crystal display module MDL will bedescribed in further detail.

<<Upper Shield Case SHD>>

FIG. 7A illustrates a front view of the upper shield case SHD, 7B aright side view of the upper shield case SHD, 7C a left side view of theupper shield case SHD, 7D a rear side view of the upper shield case SHD,and 7E a front side view of the upper shield case SHD.

The upper shield case SHD (referred to simply as a shield case) is madeby the press forming technique, i.e., blanking and bending a singlemetal plate. Symbol WD denotes an opening to expose the display area ofthe liquid crystal display element PNL and will be referred to as adisplay window. NL denotes a fixing claw for locking together the shieldcase SHD and the lower shield cases LF1, LF2, and HK denotes a hook holefor fixing. The fixing claw and the hook hole are formed integrally tothe shield case SHD. The fixing claw NL shown in FIG. 7 is in a statebeing before bent. FG2 is a frame ground, a projection of a bent metalplate, provided for electrical connection with the ground line of thescan signal line-side flexible printed circuit board FPC1 provided belowthe frame ground FG2. FG3 denotes also a frame ground for electricalconnection with the ground line of the interface printed circuit boardPCB. HLD1, HLD2, HLD3 and HLD4 denote mounting holes formed in theshield case SHD.

The shield case SHD covers the drive circuit of the liquid crystaldisplay element PNL to shield it against harmful electromagneticinterference (EMI) emitted from the liquid crystal display module.

<<Mold Case ML>>

FIG. 8A is a front view of the mold case ML, 8B a left side view of themold case ML, FIG. 8C a right side view of the mold case ML, FIG. 8D afront side view of the mold case ML, and FIG. 8E a rear side view of themold case ML. FIG. 9 is a bottom view of the mold case ML. A crosssection taken along the line I—I of FIG. 8A is shown in FIG. 10A. Across section taken along the line II—II of FIG. 8A is shown in FIG.10C. A cross section taken along the line III—III of FIG. 8B is shown inFIG. 10B. A cross section taken along the line IV—IV of FIG. 8A is shownin FIG. 10D. A cross section taken along the line V—V of FIG. 8A isshown in FIG. 10E. A cross section taken along the line VI—VI of FIG. 8Ais shown in FIG. 10F. A cross section taken along the line VII—VII ofFIG. 9 is shown in FIG. 10G.

The mold case ML has a function of the lower case of the liquid crystaldisplay module MDL, accommodates the backlight, and holds the lightguide plate GLB and the reflection sheet RFS. The mold case ML is madeby molding synthetic resin in one piece by using one molding die. Themold case ML can be firmly joined to the upper shield case SHD by meansof the fixing members and through the action of the elastic members, andhence the vibratory impact resistance and heat shock resistance areimproved, enhancing the reliability.

In the bottom surface of the mold case ML, an opening portion MO isformed at the central part except for the peripheral frame portion. Byproviding the opening portion MO at the bottom of the mold case ML, thebottom of the mold case ML can be prevented from bending outward,keeping the maximum thickness of the liquid crystal display module MDLfrom increasing. Further, the provision of the opening portion MO at thebottom of the mold case ML, also minimizes the weight of the openingportion MO made of synthetic resin in one piece, reducing the weight ofthe liquid crystal display module MDL.

Symbol HLD1, HLD2, HLD3 and HLD4 in FIG. 8A and FIG. 9 denote mountingholes formed in the mold case ML. The shield case SHD also has mountingholes at locations aligned with the corresponding holes of the mold caseML. Screws are passed through the mounting holes of the shield case SHDand mold case ML to secure and mount them to a product to which theliquid crystal display device is applied. RE denotes a part forpositioning the light guide plate GLB and the reflection sheet RFS andis formed as recesses, into which projections provided to the lightguide plate GLB and the reflection sheet RFS are fitted to mount thelight guide plate GLB and the reflection sheet RFS in the correctorientation on the mold case ML. The positioning recess RE also preventsthe light guide plate GLB and the reflection sheet RFS from beingdisplaced in the mold case ML. Further, the positioning recess RE isalso used for positioning the diffusion sheet SPS, the prism sheet PRSand the polarizing reflection plate POR. NR denotes a receiving part forreceiving the fixing claw NL of the upper shield case SHD and is formedas a recess in the mold case ML. By inserting the fixing claw NL of theshield case SHD through the lower shield cases LF1, LF2, folding it andfitting it in the receiving part NR, the shield case SHD can be firmlyjoined to the mold case ML and lower shield cases LF1, LF2. NH denotes ahook hole formed in the mold case ML. The hook hole NH is a hole throughwhich the hook provided to the frame spacer WSPC is passed, and the hookthat is passed through the hook hole NH engages with the mold case ML tojoin the frame spacer WSPC to the mold case ML firmly. The surface ofthe mold case ML that holds the reflection sheet RFS and the light guideplate GLB is inclined as shown in FIG. 10A. In this embodiment, becausethe light guide plate GLB is tapered, the mold case ML that holds thelight guide plate GLB is also provided with a slope according to thetaper of the light guide plate GLB. The mold case ML is formed at itsback with a notch MNOT at a location that, when the video signalline-side flexible printed circuit board FPC2 is bent, faces theposition of the chip parts EP mounted on the FPC2.

<<Frame Spacer WSPC>>

FIG. 11A is a front view of the frame spacer WSPC, FIG. 11B a left sideview of the frame spacer WSPC, FIG. 11C a right side view of the framespacer WSPC, FIG. 11D a front side view of the frame spacer WSPC, andFIG. 11E a rear side view of the frame spacer WSPC. FIG. 12 shows abottom view of the frame spacer WSPC. A cross section taken along theline I—I of FIG. 11D is shown in FIG. 13A. A cross section taken alongthe line II—II of FIG. 11D is shown in FIG. 13B. A cross section takenalong the line III—III of FIG. 11C is shown in FIG. 13C. A cross sectiontaken along the line IV—IV of FIG. 11C is shown in FIG. 13D. A crosssection taken along the line V—V of FIG. 11A is shown in FIG. 13E. Across section taken along the line VI—VI of FIG. 11A is shown in FIG.13F.

The frame spacer WSPC is made by molding synthetic resin in one piece byusing a single molding die. The frame spacer WSPC has a function ofsecuring the light guide plate GLB to the mold case ML to prevent thelight guide plate GLB from butting against the liquid crystal displayelement PNL. In this embodiment, the frame spacer WSPC also secures thepolarizing reflection plate POR, the prism sheet PRS and the diffusionsheet SPS to the mold case ML to prevent them from coming into contactwith the liquid crystal display element PNL. Further, the frame spacerWSPC also holds the peripheral parts of the polarizing reflection platePOR, the prism sheet PRS and the diffusion sheet SPS to prevent themfrom curving, so that the backlight can illuminate the liquid crystaldisplay element PNL uniformly. The frame spacer WSPC is colored black toprevent light 30 from the backlight from being reflected by the WSPC andadversely affecting the display. The frame spacer WSPC is colored blackby forming it out of a black resin, mixing pigments such as carbon blackin the resin, or coating the surface with a flat black paint. In FIG. 11and FIG. 12, symbol WO denotes an opening provided in the frame spacerWSPC through which the light from the backlight illuminats the liquidcrystal display element PNL. FK denotes a hook provided to the framespacer WSPC that fits into the hook hole NH of the opening portion MO tofirmly join the frame spacer WSPC to the opening portion MO.

<<Lower Shield Case LF1, LF2>>

FIG. 14A shows a front view of the lower shield case LF1, FIG. 14C is aright side view of the lower shield case LF1, FIG. 14B is a left sideview of the lower shield case LF1, and FIG. 14D is a front side view ofthe lower shield case LF1.

FIG. 15A shows a front view of the lower shield case LF2, FIG. 15C is aright side view of the lower shield case LF2, FIG. 15B is a left sideview of the lower shield case LF2, FIG. 15D is a front side view of theshield case LF2, and FIG. 15E is a rear side view of the lower shieldcase LF2.

The lower shield cases LF1, LF2 are made by a press forming technique,i.e., by blanking and bending a single metal plate.

The first lower shield case LF1 and the second lower shield case LF2cover the bottom surface of the mold case ML and have the function ofblocking harmful electromagnetic waves EMI emitted from the liquidcrystal display module MDL.

The first lower shield case LF1 receives a bent claw NL of the shieldcase SHD at its claw receiving portion NRM and secured to the liquidcrystal display module MDL. The first lower shield case LF1 is alsosecured to the mold case ML by inserting screws through the screw holesNHM1 and screw notches NHM2.

The second lower shield case LF2, too, receives a bent claw NL of theshield case SHD at its claw receiving portion NRM and secured to theliquid crystal display module MDL.

HLD1, HLD2, HLD3 and HLD4 of FIGS. 14A and 15A denote mounting holesformed in the lower shield cases LF1, LF2. The shield case SHD and moldcase ML, too, have mounting holes aligned with the corresponding holesof the lower shield cases LF1, LF2. Screws are inserted through themounting holes of the shield case SHD, the mold case ML and the lowershield cases LF1, LF2 to fasten and mount them to a product to which theliquid crystal display device is applied.

The second lower shield case LF2 also has the function of holding thebent video signal line-side flexible printed circuit board FPC2 as shownin FIG. 4A.

Symbol FG1 denotes a frame ground provided to the second lower shieldcase LF2 so as to electrically connect the case LF2 with the ground lineof the FPC2. An enlarged view of part I enclosed by a dashed line ofFIG. 15A is shown in FIG. 15F. A cross section taken along the lineII—II of FIG. 15F is shown in FIG. 15G. The frame ground FG1 isfabricated by a press forming technique) i.e., blanking and bending ametal plate.

FK denotes a hook. A cross section taken along the line III—III of FIG.15E is shown in FIG. 15H. The hook FK is hooked in the hook hole HKformed in the shield case SHD to couple the second lower shield case LF2to the shield case SHD.

The second lower shield case LF2 is corrugated for reinforcement. Across section taken along the line IV—IV of FIG. 15A is shown in FIG.151. The second lower shield case LF2 has the corrugated portion of FIG.151 along a long side. The first lower shield case LF1 and the shieldcase SHD, too, are provided with corrugated portions for reinforcement.

<<Prism Sheet PRS>>

The prism sheet PRS comprises two prism sheets-a first prism sheet PRS1and a second prism sheet PRS2. The plan view of the first prism sheetPRS1 is shown in FIG. 16A and the plan view of the second prism sheetPRS2 is shown in FIG. 17A. The prism sheet PRS is made of a transparentfilm, and at least one of its surfaces is provided with prism groovesPRR. The prism sheet PRS collects light coming from the light guideplate GLB and improves the luminance of the backlight. The first prismsheet PRS1 is provided with a prism groove PRR of FIG. 16B when viewedfrom the direction of the arrow of FIG. 16A and collects light in thedirection of the long side of the first prism sheet PRS1. The secondprism sheet PRS2 has prism grooves PRR of FIG. 17 when viewed from thedirection of the arrow of FIG. 17A and collects light in the directionof the short side of the second prism sheet PRS2. Because the lightcollecting directions of the first prism sheet PRS1 and the second prismsheet PRS2 differ, it is possible to collect light in any direction bystacking the first prism sheet PRS1 and the second prism sheet PRS2.

The first prism sheet PRS1 and the second prism sheet PRS2 are stackedone on the other, with one surface of the film not provided with theprism grooves PRR facing the other surface provided with the prismgrooves PRR. This arrangement prevents deterioration of display qualitycaused by the so-called Newton's rings—the fringes produced by theinterference between the light reflected from the surface of the firstprism sheet PRS1 and the light reflected from the surface of the secondprism sheet PRS2.

Symbol PJ1 and PJ2 denote projections to align the directions ofmounting of the first and second prism sheets PRS1, PRS2 and havedifferent shapes to distinguish the PRS1 and the PRS2.

<<Polarizing Reflection Plate POR>>

FIG. 18 is the plan view of the polarizing reflection plate POR. Thepolarizing reflection plate POR is made of plastic film, and has aproperty to transmit only polarized light with a specific polarizingaxis and reflect polarized light with other polarizing axes.

A known example of the polarizing element is the one that uses thecholesteric liquid crystal disclosed in U.S. Pat. No. 5,325,218. Otherexamples of polarizing element are found in Japanese Patent Laid-OpenNo. 212104/1992, 30816/1990, 168626/1988, and U.S. Pat. No. 5,333,072.The polarizing axis of light which the polarizing reflection plate PORtransmits is called a transmission axis. In this embodiment, thetransmission axis TAX of the polarizing reflection plate POR is alignedwith the transmission axis of the polarizing plate POL2 which isprovided on the surface of the liquid crystal display element PNLilluminated by the backlight. Hence, the light emerging from thepolarizing reflection plate POR passes through the lower polarizingplate POL2 without being absorbed by it, and thus the amount of lightpassing through the liquid crystal display element PNL increases. Thelight reflected by the polarizing reflection plate POR is returnedtoward the light guide plate GLB side, i.e., the light source side and,while the light goes back and forth between the polarizing reflectionplate POR and the light source side, it is converted into light that canpass through the polarizing reflection plate POR, i.e., the light thatcan pass through the polarizing plate POL2, thus improving the emissionefficiency of the backlight. Hence, the polarizing reflection plate PORminimizes the power consumption and improves the luminance of the liquidcrystal display module MDL. Because the light emerging from thepolarizing reflection plate POR is polarized light, it is possible toomit the polarizing plate POL2 by aligning the transmission axis TAX ofthe polarizing reflection plate POR with the orientation direction ofthe orientation film of the liquid crystal display element PNL.

PJ3, PJ4 and PJ8 denote projections to ensure that the polarizingreflection plate POR is mounted in a predetermined direction. Todistinguish the polarizing reflection plate POR from other optical filmssuch as the first prism sheet PRS1 and second prism sheet PRS2, thesetwo or more projections are different in shape from PJ1 and PJ2. Thepolarizing reflection plate POR needs to be precisely aligned with thelower polarizing plate POL2 and the orientation film of the liquidcrystal display element PNL, and therefore the alignment is made atthree points. By aligning the POR at two or more points, it is possibleto prevent the polarizing reflection plate POR from being rotated andthe transmission axis of the POR from becoming out of alignment with thepolarizing axis of the POL2 and the orientation axis of the orientationfilm.

<<Fluorescent Tube LP>>

A plan view of the fluorescent tube LP is shown in FIG. 19A and a sideview is shown in FIG. 19B. A cross section taken along the line II—II ofFIG. 19A is shown in FIG. 19C. The fluorescent tube LP contains gassealed in a glass tube whose inner surface is coated with phosphor. E1and E2 denote electrodes. When a voltage is applied to the E1 and E2, adischarge occurs in the tube causing the fluorescent tube LP to emitlight. The electrodes of the fluorescent tube LP have polarities, a highvoltage side (hot side) and a low voltage side (cold side). In thisexample the electrode E1 is the high voltage side and the electrode E2is the low voltage side. LPSOL denotes solder provided to the electrodesof the fluorescent tube LP. The electrodes El, E2 are connected to thelamp cable LPC3 by the solder LPSOL.

<<Lamp Cable LPC3>>

A plan view of the lamp cable LPC3 for supplying electricity to thefluorescent tube LP is shown in FIG. 20A. A cross section taken alongthe line I—I is shown in FIG. 20B. An enlarged view of part II enclosedby a dashed line is shown in FIG. 20C.

The lamp cable LPC3 is installed in the liquid crystal display moduleMDL and is formed as a flat cable to reduce the installation space asshown in FIG. 4. The lamp cable LPC3 has a construction in which a metalfoil conductor LY is sandwiched between plastic films BSF1, BSF2, sothat it can be bent flexibly. BYD denotes a bonding agent to bond theplastic films BSF1, BSF2 and the metal foil conductor LY together. Theplastic film BSF1 has a double-sided adhesive tape BAT attached to itsupper surface, so that it can be secured to another member, such as thelamp reflector LS as shown in FIG. 1A. TRM2 denotes a terminal that isconnected to the electrode E1 or E2 of the fluorescent tube LP by thesolder LPSOL. The terminal TRM2 has an elongate shape, for example anelliptical one, so that when it is soldered to the electrode E1 or E2,the solder LPSOL is exposed and seen as shown in FIG. 1C. Hence, thecondition of the solder connection can be checked. The terminal TRM2 isconnected to the low voltage side terminal E2 to reduce powerconsumption. TMR1 denotes a terminal that is connected to the lamp cableLPC2 led out of the shield case, as shown in FIG. 1B. One of the plasticfilms BSF1, BSF2 may be an insulating paint.

<<Rubber Bushings GB1, GB2>>

The rubber bushings GB1, GB2 holding the fluorescent tube LP are shownin FIGS. 21A, 21B, 21C, 21D, 21E, 22A, 22B and 22C. FIG. 21Aillustrates, as viewed from one direction, the rubber bushing GB1 thatholds the fluorescent tube LP on the side where the fluorescent tube LPis connected with the lamp cable LPC3. FIG. 21B is a view as viewed fromdirection 1 and FIG. 21C is a view as viewed from direction 2. A crosssection taken along the line I—I is shown in FIG. 21D and a crosssection taken along the line II—II is shown in FIG. 21E.

FIG. 22A shows the rubber bushing GB1 holding one end of the fluorescenttube LP and the second rubber bushing GB2 holding the other end, asviewed from one direction. FIG. 22B shows the rubber bushings GB1, GB2as viewed from direction 1 and FIG. 22C shows them as viewed fromdirection 2.

FIG. 1A shows rubber bushings GB1 and GB2, which hold the fluorescenttube LP.

The rubber bushings GB1, GB2 are made of an insulating elastic materialsuch as rubber to protect the fluorescent tube LP against vibrations andimpacts. Because the rubber bushings GB1, GB2 are each provided with aslit HOPG through which the lamp cables LPC3 and LPC1 are passed, thework of covering the rubber bushings GB1, GB2 over the electrodes of thefluorescent tube LP after connecting the lamp cables LPC3, LPC1 to theseelectrodes can be done easily. The rubber bushings GB1, GB2 are, asshown in FIG. 1A, fitted into the lamp reflector LS to fix thefluorescent tube LP. The rubber bushing GB2 is provided with a notch toaccommodate the connecting portion between the lamp cable LPC2 and thelamp cable LPC3, as shown in FIG. 1A.

<<Lamp Reflector LS>>

FIG. 23A shows the lamp reflector LS, as viewed from one direction,which reflects light from the fluorescent tube LP and directs light tothe light guide plate GLB. The lamp reflector LS as viewed fromdirection 1 is shown in FIG. 23B. A cross section taken along the lineI—I is shown in FIG. 24A, a cross section along the line II—II is shownin FIG. 24B, and a cross section along the line III—III is shown in FIG.24C.

Silver is deposited on the surface of the lamp reflector LS on which thefluorescent tube LP is provided by vacuum evaporation to enhance thelight reflectance. The lamp reflector LS is U-shaped in cross section tohold the fluorescent tube LP through the rubber bushings GB1, GB2, andmade by bending a stiff metal plate, such as a brass plate.

The lamp reflector LS may be made by bending an aluminum plate. Whenaluminum is used for the lamp reflector LS, a light reflection surfacecan be formed by surface-processing the surface on which the fluorescenttube LP is installed. The lamp reflector LS made of aluminum ischaracterized by a low parts cost but is inferior in terms of the lightreflectance (or light emitting efficiency of the backlight) to the lampreflector LS whose reflection surface is silver-vaporized.

The lamp reflector LS has a slit HOPS through which the lamp cable LPC3is passed. As shown in FIG. 1B, the lamp cable LPC3, after beingconnected to the electrode E2 of the fluorescent tube LP, is passedthrough the slit of the rubber bushing GB1 and the slit HOPS to come outof the lamp reflector LS. The lamp cable LPC3 that is led out of thelamp reflector LS is, as shown in FIG. 1A, led along the outside of thelamp reflector LS to the rubber bushing GB2 side and is connected to thelamp cable LPC2. Hence, because the space between the lamp cable LPC3and the fluorescent tube LP is maintained by the lamp reflector LS,there is no risk that the luminance of the fluorescent tube LP decreasesor power consumption increases due to a leakage current between the lampcable LPC3 and the fluorescent tube LP.

Further, as shown in FIG. 1A, because the lamp reflector LS supports therubber bushings GB1, GB2 and the lamp cable LPC3 is secured to the lampreflector LS with the double-sided adhesive tape BAT, it is possible tohandle the fluorescent tube LP, the rubber bushings GB1, GB2, the lampreflector LS and the lamp cable LPC3 as one lamp unit, making theassembly of the liquid crystal display module and the replacement of thefluorescent tube easy.

<<O-Ring OL>>

FIG. 25A shows the O-ring OL that prevents the fluorescent tube LP fromcoming into contact with the lamp reflector LS. A cross section takenalong the line I—I is shown in FIG. 25B.

The fluorescent tube LP fitted in the center hole of the O-ring OL is,as shown in FIG. 1A, installed together with the O-ring OL inside thelamp reflector LS. The O-ring OL thus prevents the contact between thefluorescent tube LP and the lamp reflector LS. The O-ring OL is made ofa transparent elastic material, such as silicone rubber, to ensure thatthe luminance of the fluorescent tube LP at locations where the O-ringsOL are installed is not lowered.

<<Light Guide Plate GLB>>

FIG. 26 shows a unit that combines the light guide plate GLB, thereflection sheet RFS and the diffusion sheet SPS. FIG. 26A is a planview of the unit of the GLB, RFS and SPS, as viewed from the diffusionsheet SPS side. FIG. 26B is a side view of the unit.

FIG. 27 is a plan view of the light guide plate GLB that guides lightfrom the fluorescent tube LP and forms a surface light source. FIG. 27Bis a side view as viewed from direction 1. The light guide plate GLB isformed of a transparent solid material, such as acrylic resin. On one ofthe surfaces SF1 of the light guide plate GLB a pattern DOT (forexample, a dot pattern) is formed by printing or the like, so that thelight entering from the other surface SF3 is irregularly reflected bythe pattern DOT and goes out from the surface SF2 opposite to thesurface SF1. A pattern DOT2 at the corner of the light guide plate GLBis shaped like the letter L as shown in FIG. 27A. Because the cornerportions of the light guide plate GLB decrease in luminance, theL-shaped patterns DOT2 are provided at the corners of the light guideplate GLB to enhance the luminance by increasing the area of irregularreflection, PJ5 denotes projections provided to the light guide plateGLB which are intended to define the direction in which the light guideplate GLB is mounted on the mold case ML and to prevent the light guideplate GLB from moving in the mold case ML. The projections PJ5 havecurved surfaces R at their bases on the body of the light guide plateGLB to minimize the risk of breakage due to impacts. ARM denotes amarker on the surface SF1 side to indicate the surface to be printedwith the pattern DOT. The marker ARM is provided not only in theeffective area (where the pattern DOT is formed) but also in other areassuch as the projection PJ5 to maintain uniformity of the light emergingfrom the light guide plate GLB. As shown in FIG. 26A and 26B, the sidesurface of the light guide plate GLB, except for the light incidentsurface SF3, is provided with an end-face tape SDT, which is made of awhite film to return the light coming out of the side surface of thelight guide plate GLB to the GLB.

<<Reflection Sheet RFS>>

As shown in FIG. 26B, the reflection sheet RFS is laid over the surfaceSF1 of the light guide plate GLB where the pattern DOT is formed.

FIG. 28A is a plan view of the reflection sheet RFS, and FIG. 28B is aside view of the reflection sheet RFS as viewed from direction 1. Thereflection sheet RFS is made of a white film to return the light comingout of the surface SF1 of the light guide plate GLB, where the patternDOT is formed, to the light guide plate GLB.

Symbol PJ6 denotes projections provided to the reflection sheet RFSwhich are intended to define the direction in which the reflection sheetRFS is mounted on the mold case ML and to prevent the reflection sheetRFS from moving in the mold case ML. GER denotes a gray printed pattern,and BAT denotes a double-sided adhesive tape. As shown in FIG. 26B, thereflection sheet RFS is bonded to the light guide plate GLB with thedouble-sided adhesive tape BAT in such a way that the gray printedpattern GER is on the light incident surface SF3 of the light guideplate GLB. The reason why the gray printed pattern GER is placed on thelight incident surface SF3 of the light guide plate GLB is to preventthe generation of so-called bright lines that increase the luminance onthe light incident surface SF3 side compared with other regions of thelight guide plate GLB.

<<Diffusion Sheet SPS>>

As shown in FIG. 26B, the diffusion sheet SPS is laid over the surfaceSF2 of the light guide plate GLB from which light is sent out. Thereflection sheet RFS diffuses the light coming out of the surface SF2 ofthe light guide plate GLB to form a uniform surface light source.

FIG. 29A shows a plan view of the diffusion sheet SPS and FIG. 29B is aside view of the diffusion sheet SPS as viewed from direction 1. Thediffusion sheet SPS is made by roughening the surface of a transparentfilm. PJ7 denotes projections provided to the diffusion sheet SPS whichare intended to define the direction in which the diffusion sheet SPS ismounted on the mold case ML and to prevent the diffusion sheet SPS frommoving in the mold case ML.

FIG. 29C is an enlarged view of part I, and FIG. 29D an enlarged view ofpart II. BLK denotes a black printed pattern BLK, and BAT denotes adouble-sided adhesive tape. The double-sided 30 adhesive tape BAT isprovided in the area where the black printed pattern BLK is formed. Asshown in FIG. 26B, the diffusion sheet SPS is bonded to the light guideplate GLB with the double-sided adhesive tape BAT in such a way that theblack printed pattern BLK is on the light incident surface SF3 of thelight guide plate GLB. The reason why the diffusion sheet SPS isprovided with the black printed pattern BLK on the light incidentsurface SF3 side of the light guide plate GLB is to prevent thegeneration of generally-called bright lines.

The rough surface of the diffusion sheet SPS is provided on the sideopposite to the surface facing the light guide plate GLB. That is, inthis embodiment, the prism sheet PRS is laid over the diffusion sheetSPS and the rough surface of the diffusion sheet SPS is provided on thesurface facing the prism sheet PRS, as shown in FIG. 4A. Roughening thesurface of the diffusion sheet SPS facing the prism sheet PRS canprevent the generation of Newton's rings described earlier on thecontact surface between the diffusion sheet SPS and the prism sheet PRS.

<<Liquid Crystal Display Element PNL>>

FIG. 30 shows the scan signal line-side flexible printed circuit boardFPC1 and the video signal line-side flexible printed circuit board FPC2before being bent, both mounted at the peripheral part of the liquidcrystal display element PNL.

FIG. 34 is an enlarged view of a portion where the liquid crystaldisplay element PNL is connected with the flexible printed circuitboards FPC1, FPC2.

FIG. 35 is a cross section taken along the line I—I of FIG. 34.

IC1 denotes a drain driver chip and IC2 denotes a gate driver chip.

In this embodiment, the driver chips IC1, IC2 are directly mounted onthe substrate of the liquid crystal display element PNL by using theanisotropic conductive films ACF1, ACF2 and an ultraviolet setting resin(chip-on-glass mounting: COG mounting), as shown in FIG. 35. The COGmounting is suited for a high resolution liquid crystal display elementPNL with large numbers of pixels. For a tape carrier package mountedwith driver IC chips, for example, the connection of the driver chipswith the liquid crystal display element PNL is difficult when thedistance between the connection terminals becomes smaller than 100microns due to elongation and shrinkage of the tape carrier film. Forthe COG mounting, however, connection can be made between the drive ICchips and the liquid crystal display element PNL even if the distancebetween the connection terminals DTM and GTM is less than 70 microns.

In this embodiment, the drain driver chips IC1 are arranged in a rowalong one long side of the liquid crystal display element PNL and thedrain lines are led out to the long side. The pitch between the gatelines is relatively large, so that in this embodiment the terminals GTMare led out at one short side. If the definition becomes higher, thegate terminals GTM may be led out at the two opposite shorter sides.

In a system where the drain lines and the gate lines are alternately ledout, although the connection between the drain terminals DTM or the gateterminals GTM and the bumps BUMP on the output side of the drive ICsbecomes easy, a need arises to arrange the peripheral circuit boards atthe peripheral portions along the two opposing long sides of the liquidcrystal display element PNL, making the external dimension larger thanthat of the system where the terminals are led out at one side. Thus,this embodiment employs a multilayer flexible board and the drain linesare led out to only one side to reduce the picture-frame area.

<<Scan Signal Line-Side Flexible Printed Circuit Board FPC1>>

FIG. 31A is a plan view of the scan signal line-side flexible printedcircuit board FPC1 that supplies electricity and signals to the gatedriver chip IC2. FIG. 31B is an enlarged plan view of a portion of thescan signal line-side flexible printed circuit board FPC1 that isconnected to the terminal of the liquid crystal display element PNL.

J1 to J8 denote first terminals of the divided connecting portions. FIILdenotes holes for positional alignment. EP denotes chip parts such asresistors and capacitors. TM denotes metal leads. ALMD denotes alignmentmarks for positional alignment between the FPC1 and the liquid crystaldisplay element PNL. BF1 and BF2 denote base films of the scan signalline-side flexible printed circuit board FPC1. The metal leads TM of theconnecting portions are provided on the base film BF1 and exposed fromthe base film BF2. CT3 denotes a connector to make electrical connectionwith the interface printed circuit board PCB.

FIG. 34 shows the scan signal line-side flexible printed circuit boardFPC1 connected to the liquid crystal display element PNL.

<<Video Signal Line-Side Flexible Printed Circuit Board FPC2>>

FIG. 32 shows a plan view of the video signal line-side flexible printedcircuit board FPC2 that supplies electricity and signals to the draindriver chip IC1.

J1 to J14 denote first terminals of divided connecting portions. Likethe FPC1, the connecting portions of the FPC2 have the structure of FIG.31B. A part a of the FPC2 is a bent portion formed thin so that it canbe bent easily. A part b of the FPC2 is a multilayer wiring portion inwhich two or more wiring layers are formed in multilayer to increase thewiring density. FHL denotes holes for positional alignment. EP denoteschip parts EP such as resistors and capacitors. HOP denotes an openingprovided in the FPC2.

FGP denotes a frame ground pad FGP electrically connected to the groundline of the video signal line-side flexible printed circuit board FPC2.In the frame ground pad FGP a conductive foil which is electricallyconnected to the ground line is exposed from the base film of the FPC2and is in contact with the frame ground FG1 of the lower shield case LF2to electrically connect the ground line of FPC2 to the LF2. The videosignal line-side flexible printed circuit board FPC2 supplies videosignals to the drain driver chip IC1, and hence high-frequency currentflows through the wiring of the board FPC2, giving rise to a possibilityof electromagnetic waves being emitted from the FPC2. In thisembodiment, a plurality of frame ground pads FGP are provided on theFPC2 and electrically connected to the lower shield case LF2 coveringthe FPC2, so that the electromagnetic waves emitted from the FPC2 areblocked by the lower shield case LF2, thus eliminating EMI.

CT4 denotes a connector for electrical connection with the interfaceprinted circuit board PCB. On the back side of a part of the FPC2 wherethe connector CT4 is mounted, a hard plate SUP such as a glass epoxyboard is attached to facilitate the connection of the connector CT4 tothe connector of the interface printed circuit board PCB.

FIG. 34 shows the FPC2 connected to the liquid crystal display elementPNL.

<<Interface Printed Circuit Board PCB>>

FIG. 33 shows a plan view of the interface printed circuit board PCBthat receives a display signal from the host computer and controls thescan signal line drive circuit and the video signal line drive circuitto display data on the liquid crystal display element PNL. The interfaceprinted circuit board PCB has a plurality of electronic parts mounted ona multilayer printed circuit board, such as a multilayer board of glassepoxy resin. CT1 denotes an interface connector which makes electricalconnection with external devices of the liquid crystal display moduleMDL, such as a computer. LVDS denotes a signal converter that convertssignals sent from external devices into signals that can be processed bythe liquid crystal display device. In this embodiment, display signalssupplied from an external device are digital signals. Although, in thecase of a CRT display, analog signals are more advantageously employedas the display signals supplied from an external device, the liquidcrystal display device can use display signals sent from the externaldevice more advantageously if they are digital signals because the draindriver chip that outputs video signals to the liquid crystal displayelement is a digital driver. Further, by making the display signalsdigital, the signal converter LVDS can send the display signals from thehost computer to the liquid crystal module efficiently, reducing thenumber of signal lines in the cable for transferring the display signalsand reducing EMI. TCON denotes a controller that controls the scansignal line drive circuit and the video signal line drive circuitaccording to the display signals converted by the signal converter LVDSand displays data on the liquid crystal display element PNL. The numberof connection terminals of the controller TCON increases with the numberof gradation levels, so that in this embodiment the IC chip of TCON ismounted in the BGA (ball grid array) package, which mounted on theinterface printed circuit board PCB. CTR4 denotes a connector forconnection with the connector CT4 of the FPC2.

In this embodiment, because the signal converter LVDS and the controllerTCON are mounted in this order between the interface connector CT1 andthe connector CTR4 on the interface printed circuit board PCB, the flowsof the display signals are aligned in the direction of the arrow,eliminating redundancy in the wiring layout and reducing the size of theinterface printed circuit board PCB and therefore the frame area of theliquid crystal display module. HI denotes a hybrid IC having electroniccircuits integrated on a child board. In this embodiment, the HI has anintegrated power supply circuit that supplies electricity to thecontroller TCON, the signal converter LVDS, the gate driver chip IC2 andthe drain driver chip IC1. CTR3 denotes a connector CTR3 connected withthe connector CT3 of the FPC1. The connection between the FPC1 and thePCB and between the FPC2 and the PCB is made by bending the FPC1 andFPC2 and inserting their connectors into the connectors of the PCB, asshown in FIG. 30. FGP is a frame ground pad electrically connected tothe ground line of the PCB and is used to make an electrical connectionwith the upper shield case SHD. The interface printed circuit board PCB,because it processes video signals, has a possibility thathigh-frequency current flowing through the circuit wiring can emitelectromagnetic waves. Thus, this embodiment connects the shield caseSHD covering the PCB to the ground of the PCB at the frame ground padFGP to eliminate EMI.

<<Equivalent Circuit of the Liquid Crystal Display Module>>

FIG. 36 is a block diagram showing an equivalent circuit of the liquidcrystal display module MDL. A video signal line drive circuit 103 isprovided only under the TFT liquid crystal display element TFT-LCD. Onthe side surfaces of the TFT-LCD are arranged a scan signal line drivecircuit 104, a controller 101 and a power supply circuit 102. The videosignal line drive circuit 103 is mounted by bending the multilayerflexible board, as described earlier, to reduce the picture-frame areaof the liquid crystal display module MDL.

The controller 101 and the power supply circuit 102 are mounted on themultilayer printed circuit board (interface printed circuit board PCB).The interface printed circuit board PCB mounted with the elements 101and 102 is stacked under the back of the scan signal line drive circuit104 to reduce the picture-frame area of the liquid crystal displaymodule MDL.

As shown in FIG. 36, the thin film transistor TFT is provided in anintersecting region between two adjacent drain signal lines DL and twoadjacent gate signal lines GL. The drain electrode and the gateelectrode of the thin film transistor TFT are connected to the DL andthe GL, respectively. The source and the drain are determinedfundamentally by the bias polarity between them. In the circuit of thisliquid crystal display device, the polarity is inverted during operationand it should be understood that the source electrode is alternatelychanged. In the following description, however, the electrode connectedto the DL is fixedly a drain electrode and the electrode connected tothe pixel electrode is a source electrode.

The source electrode of the thin film transistor TFT is connected to thepixel electrode. Since a liquid crystal layer is provided between thepixel electrode and the common electrode, a voltage is applied from thepixel electrode to the liquid crystal layer.

The thin film transistor TFT becomes conductive when a positive biasvoltage is applied to the gate electrode and becomes non-conductive whena negative bias voltage is applied to the gate electrode. Thus, it ispossible to select a pixel electrode to which a video signal is to beapplied through the drain signal line DL by controlling the voltageapplied to each gate signal line GL.

FIG. 44 shows drive waveforms of the TFT liquid crystal display elementTFT-LCD of FIG. 36. VG denotes a voltage waveform applied to the gatesignal line GL, VCOM denotes a voltage waveform applied to the commonelectrode, VDH denotes a voltage waveform applied to odd-numbered drainsignal lines DL, and VDL is a voltage waveform applied to even-numbereddrain signal lines DL. VG denotes a period of one frame and changes inits level between high and low, and at the timing that the VG goes low,the voltages VDH, VDL are written into the pixel electrodes. Thevoltages VDH and VDL change signal polarities in the cycle of onehorizontal scan 1H with VCOM as their center. The voltage VDH and VDLchange signal polarities in one frame cycle, too. Further, VDH and VDLare in the relation of opposite polarity. By performing the drive method(dot inversion drive) shown in FIG. 44, a problem is solved that thesignals of GL or DL leak into unrelated pixel electrodes to degrade thedisplay quality of the liquid crystal display module MDL. Further,because the drain driver chip IC1 of the video signal line drive circuit103 has a function of changing the polarities of the odd-numbered outputand the even-numbered output and outputting both of them simultaneously,the dot inversion drive that ensures good display quality can beperformed and the video signal line drive circuit 103 is provided at oneside of the liquid crystal display module MDL to reduce thepicture-frame area. It is noted that FIG. 44 shows VCOM in an ideal casewhere there is no coupling between the gate electrode and the sourceelectrode of the thin film transistor TFT. Actually, however, a bias tocancel the coupling is applied to VCOM.

Between a pixel electrode and a GL that selects a preceding stage pixelelectrode is connected a capacitor Cadd that holds a voltage of thepixel electrode. It is also possible to form a capacitive line differentfrom the gate signal line GL to provide the Cadd between the pixelelectrode and the capacitive line. In this case, to the capacitive linea voltage equivalent to the voltage applied to the common electrode isapplied.

<<Controller 101>>

FIG. 37A and FIG. 37B illustrate the flow of display data between thehost computer and the controller 101. As shown in one example of FIG.37A, the display signal output from the display controller of the hostcomputer PC is divided into two signals. The two divided signals arethen supplied to the signal converters LVDS on the sending side wherethey are converted into differential signals, which are sent through acable to the interface connector CT1 of the liquid crystal displaymodule MDL. The controller 101 transfers the two differential signalsthat are supplied to the interface connector CT1 to the respectivesignal converters LVDS on the receiving side where the differentialsignals are reconverted into two divided display signals, which are theninput to the controller TCON that controls the scan signal line drivecircuit and the video signal line drive circuit. The display signal sentfrom the display controller to the controller TCON is digital data andthe number of bits and frequency at each stage are shown in FIG. 37A.Because the display signal output from the display controller is dividedby data conversion into two before being sent to the liquid crystaldisplay module MDL, the frequency of the signals handled by the liquidcrystal display module MDL decreases, making EMI hardly occur. Thesignal converter LVDS on the PC side converts the parallelly inputdigital data into serial data and transfers them to the liquid crystaldisplay module MDL. The signal converter LVDS on the liquid crystaldisplay module MDL side converts the serial data into parallel data torecover the display signal. This arrangement reduces the number ofterminals of the interface connector CT1 to enhance the reliability ofconnection and also reduces the number of lines between the PC and theMDL and therefore the number of lines carrying high frequency currents,thus hardly generating EMI. It is noted that the differential signalsoutput from the signal converter LVDS lower the frequency by compressingthe data of the display signals and thereby prevent EMI. By providingthe liquid crystal display module MDL with a signal converter LVDS thatconverts the incoming display signal in the form of serial data intoparallel data to recover the display signal as in this embodiment,various advantages can be produced which include the ability to preventan increase in the number of terminals of the interface connector CT1even when the number of levels of gradation in the display increases andalso the ability to reduce the electromagnetic emission from the liquidcrystal display module MDL and eliminates their adverse influences onother devices.

FIG. 37B shows another example of the flow of display data between thehost and the controller 101. In this example, the data modulator thathas the function of dividing the display signal and the function ofconverting parallel data into serial data and outputting a differentialsignal is provided on the PC side, and the data demodulator thatconverts the differential signal sent from the PC into parallel data toreproduce the divided display signals is provided on the liquid crystaldisplay module MDL. The example of FIG. 37B, although it increases thefrequency of the differential signal, offers the advantage that thenumber of terminals of the interface connector CT1 decreases further,the connection reliability is enhanced, the size of the interfaceprinted circuit board PCB can be reduced, and the picture-frame area ofthe liquid crystal display module MDL can be reduced.

<<Power Supply Circuit 102>>

FIG. 38 illustrates the supply of electricity to the liquid crystaldisplay module MDL. A part enclosed by a dashed line in FIG. 38 belongsto the power supply circuit. The power supply circuit converts a voltagesupplied through a power source terminal of the interface connector CT1into voltages required by individual parts and outputs the convertedvoltages to them. Currents flowing through individual lines and appliedvoltages in the liquid crystal display module MDL are also shown in FIG.38. A denotes points where currents are measured. The numeric values inparentheses represent power consumption in mW. In the power supplycircuit 102 a DC-DC converter that produces a plurality of voltages hasthe largest power consumption. In this embodiment, to enhance heatdissipation of the DC-DC converter, a hybrid IC configuration isemployed in which the DC-DC converter is formed on a child printedcircuit board HI on the interface printed circuit board PCB.

<<Measures Against EMI of Controller Circuit 101 and Power SupplyCircuit 102>>

FIG. 39 shows the arrangement of filters (EMI filters) to attenuateelectromagnetic waves, the source of EMI. The EMI filters include an LCfilter, an RC filter and an R filter in the order of magnitude ofattenuation. The EMI filters attenuate high frequency components of asignal and therefore should be appropriately used according to signalfrequency, and the signal may be attenuated if not. In this embodiment,LC filters shown at (1), (2), (5) are inserted between the VDD of the DCpower source and the signal processing circuits TCON and LVDS to cut offhigh frequency components. Because the frequencies of the data line andclock line DCLK between LVDS and TCON are high, R filters are used. Thedata line between the TCON and the video signal line drive circuit 103carries signals with relatively high frequencies and thus the RC filtershown at (7) is used.

<<Thin Film Transistor Substrate SUB1 and Opposed Substrate SUB2>>

FIG. 40 shows a plan view of a pixel area of the liquid crystal displayelement PNL. A cross section along the line I—I of FIG. 40 is shown inFIG. 41; a cross section along the line II—II is shown in FIG. 42; and across section along the line III—III is shown in FIG. 43.

As shown in FIG. 40, each pixel is disposed in an intersecting regionbetween two adjacent scan signal lines GL and two adjacent video signallines DL. Each pixel includes a thin film transistor TFT, a pixelelectrode ITO1 and a capacitor Cadd. As shown in FIG. 42, the thin filmtransistor TFT and the transparent pixel electrode ITO1 are formed onthe first transparent glass substrate SUB1 side of the liquid crystallayer. On the second transparent glass substrate SUB2 side there areformed a color filter FIL and a light shielding black matrix pattern BMare formed. On both surfaces of each substrate SUB1, SUB2 are depositedoxide silicon films SIO.

On the surface of the SUB2 on the inner side (LC side) are formed alight shielding film BM, a color filter FIL, a passivation film PSV2, atransparent common electrode ITO2 and an upper orientation film OR12 inthis order. Symbol POL1 and POL2 denote polarizing plates provided onthe outer surfaces of the SUB1 and SUB2. VINC1 and VINC2 denote viewingangle enlarging films provided on the outer surfaces of the SUB1 andSUB2.

The thin film transistor TFT is made by depositing in multilayer, asshown in FIG. 42, a gate electrode formed integrally with the scansignal lines GL, a surface oxide film AOF of the scan signal lines GL,an insulating film GI of silicon nitride, an i-type semiconductor layerAS of intrinsic amorphous silicon, an impurity-doped semiconductor layerdo, and a source electrode SD1 and a drain electrode SD2.

The thin film transistor TFT is covered with a passivation film PSV1formed of an organic film of silicon nitride and polyimide. Over thePSV2 and ITO is provided a lower orientation film ORI1.

The GL is formed of a first conductive film g1 of aluminum. Hence, thesurface oxide film AOF of the GL is made of aluminum. The GL may beformed of tantalum. If the GL is formed of tantalum, the AOF is atantalum oxide film.

The pixel electrode ITO1 is formed of a transparent conductive film d1such as an ITO (indium-tin oxide) film.

The SD1 and SD2 are formed of a multilayer film having a secondconductive film d2 of chromium and a third conductive film d3 ofaluminum. The DL is also formed of a multilayer film of d2 and d3.

The AS and GI are formed along and below the DL in addition to withinthe TFT. By forming the AS and GI along the DL, the DL is prevented frombeing broken due to the steps of the AS and GI. The GI does not coverall of the pixel area and there are portions where the GI is removed,such as parts on the ITO1. By providing the portions where the GI isremoved in the pixel area, the stresses of the GI is alleviated toprevent it from being peeled off.

Over the pixel electrode ITO1 there is an opening HOPI where thepassivation film PSV1 is removed. By providing the opening HOPI in thepassivation film PSV1, the stresses in the PSV1 is alleviated to preventit from being peeled off. Further, the provision of the HOPI over theITO1 intensifies the electric field that the ITO1 applies to the liquidcrystal layer LC.

The capacitor Cadd comprises a first electrode PL1 formed of the g1, asecond electrode PL2 formed of d1, and a dielectric film formed of theAOF. The second electrode PL2 is connected through a hole CNT formed inthe AS and GI to a wiring made of a multilayer film of d2 and d3, andthe wiring made of d2 and d3 is connected to the pixel electrode ITO1 ata portion where the AS and GI are removed, so that the PL1 and the ITO1are electrically connected. The aluminum oxide film AOF has a higherdielectric constant than those of silicon nitride and silicon oxide, andconsequently the use of a single-layer AOF film for the dielectric filmof the Cadd can reduce the size of the Cadd, thereby improving theaperture ratio of the pixel. Further, because the ends of the firstelectrode PL1 are covered with the GI and AS over which a wiringconnecting the PL2 and the ITO1 is formed, a possibility of concentratedelectric fields produced at the ends of the PL1 causing dielectricbreakdown is eliminated. Further, because the dielectric constant of thetantalum oxide film is also high, it is also possible to use tantalumfor the PL1 to form a tantalum oxide film as the AOF.

Embodiment 2

FIG. 45 shows a second embodiment of this invention. FIG. 45A is abottom view of the liquid crystal display module MDL and FIG. 45B a sideview of the liquid crystal display module MDL. In the second embodiment,the liquid crystal display module MDL is provided with rubber cushionsGC1, GC2, GC3, GC4 at the centers of its four sides for reinforcement.Provision of the rubber cushions GC1, GC2, GC3, GC4 at the centers ofthe four sides of the liquid crystal display module MDL improves thestrength of the MDL against impacts and vibrations.

Further, in the second embodiment, a cover film CBF is bonded to the MDLnear the centers of the lower long sides to fix the lower shield casesLF1, LF2. The cover film CBF bonded to the lower long sides of the MDLprevents the lower shield cases LF1, LF2 from coming off even if strongvibrations and impacts are applied to the MDL.

The other constructions of the second embodiment are the same as thoseof the first embodiment.

Embodiment 3

In a destructive test whereby a liquid crystal display device equippedwith a drain driver on one lateral side was subjected to strong impactswhich do not occur normally, a phenomenon was observed in which, asshown in FIG. 46A, the glass substrates SUB1, SUB2 on the LD side wherethe drain driver is not mounted were broken and came out from the shieldcase SHD. The investigation into the cause of the breakage of the SUB1and SUB2 has found that application of strong impacts to the liquidcrystal display module MDL caused the light guide plate GLB to buttagainst the glass substrate SUB1 which could not withstand the impactsand broke.

FIGS. 47A, 47B and 47C show cross sections of the liquid crystal displaymodule MDL where measures are taken to prevent the glass substrates ofthe liquid crystal display element PNL from being broken by strongimpacts.

In the embodiment shown in FIG. 47A, the glass substrate SUB1 and theopposing glass substrate SUB2 on the LD side are extended to formextended portions and a spacer SPC4 of rubber or vinyl chloride isprovided between the shield case SHD and the extended part of the SUB1.In the embodiment of FIG. 47A, while the spacer SPC4 absorbs to someextent the impacts applied to the SUB1, the impact concentrates on theSUB1 and the possibility still remains of the SUB1 being broken bystrong impacts.

In the embodiment shown in FIG. 47B, the glass substrate SUB1 and theopposing glass substrate SUB2 are aligned at their end portions on theLD side, and the glass substrate SUB2 and the shield case SHD are bondedtogether with a double-sided adhesive tape BAT. In the embodiment ofFIG. 47B, because the impacts that the liquid crystal display elementPNL receives are sustained by the glass substrates SUB1 and SUB2, strongimpacts greater than 200G can be tolerated. Although it is possible tobond the SUB2 to the SHD with a BAT without aligning the end portions ofthe SUB1 and SUB2, the aligning of the end portions can reduce thepicture-frame area of the liquid crystal display element PNL.

In the embodiment shown in FIG. 47C, the upper polarizing plate POL1 onthe LD side is extended from the glass substrate SUB2 to which the POL1is bonded, and the extended portion of the POL1 is bonded to the shieldcase SHD with a double-sided adhesive tape BAT. In the embodiment ofFIG. 47C, because the impacts that the liquid crystal display elementPNL receives are sustained by the glass substrates SUB1 and SUB2 and theupper polarizing plate POL1, strong impacts greater than 100G can betolerated. Further, in the embodiment of FIG. 47C, because there is noneed to cut the glass substrates so that the ends of the SUB1 and SUB2may be aligned, the fabrication of the liquid crystal display elementPNL is easy.

In the embodiment described above, the other constructions not describedare the same as those of the first embodiment.

Embodiment 4

When the liquid crystal display module MDL is subjected to strongimpacts, the light guide plate GLB is moved, as described 30 above. Thelight guide plate GLB is formed of one acrylic plate and has a greatmass, so that when subjected to impacts, the light guide plate GLB tendsto move inside the liquid crystal display module MDL by the action ofthe inertia force. Hence, when strong impacts are applied to the liquidcrystal display module MDL, the projection PJ5 that secures the lightguide plate GLB to the liquid crystal display module MDL may break.

As shown in FIG. 48, this embodiment provides the base portion of theprojection PJ5 on the light guide plate with a curved surface R forreinforcement to prevent breakage of the PJ5. With the curved surface of1.0 formed at the base of the PJ5, the PJ5 did not come off the GLB whenimpacts greater than 100G were applied.

Further, by bonding the light guide plate GLB to the mold case ML thataccommodates the GLB with a double-sided adhesive tape BAT, as shown inFIG. 48, the light guide plate GLB can be prevented from moving in theML even when strong impacts greater than 220G are applied.

The other constructions not described above are the same as those of thefirst embodiment.

Embodiment 5

In cases where the drain driver chip IC1 or gate driver chip IC2 isdirectly mounted on the glass substrate SUB1 of the liquid crystaldisplay element PNL, when the liquid crystal display element PNL is heldby the shield case SHD, there is a risk that the IC1 or IC2 will buttagainst the SHD and be broken.

An example of the liquid crystal display module MDL with a provision forpreventing breakage of the IC1 is shown in FIGS. 49A, 49B, 49C, 49D, 49Eand 49F.

FIG. 49A shows an example in which the chip IC1 on the liquid crystaldisplay element PNL is bonded to the shield case SHD with a double-sidedadhesive tape BAT. Although the PNL is firmly secured to the shield caseSHD, the impact that the shield case SHD receives is directlytransferred to the IC1, which may be destroyed.

FIG. 49B shows an example in which the PNL is secured to the SHD byattaching a double-sided adhesive tape BAT to a connecting portion ofthe PNL where the liquid crystal display element PNL and the videosignal line-side flexible printed circuit board FPC2 are stackedtogether to make electrical connection. In the example shown in FIG. 49Bthere is little possibility that the IC1 is broken but a problem remainsthat when the PNL is peeled from the SHD, the video signal line-sideflexible printed circuit board FPC2 may be peeled off the PNL.

FIGS. 49C and 49D show an example in which the vinyl chloride spacerCLSPC is provided between the drain driver chips IC1. In the example ofFIGS. 49C and 49D, because the space where the IC1s are installed issecured by the vinyl chloride spacer CLSPC, the IC1s are not damagedeven when the display device is subjected to strong impacts. In theembodiment shown in FIGS. 49C and 49D, because the portions where thevinyl chloride spacer CLSPC are in contact with the glass substrate SUB1are narrow, impacts may concentrate on the portions where the CLSPC arein contact with the SUB1 and hence may break the SUB1.

FIG. 49E represents a case where the rubber spacer GSPC is installedbetween the drain driver chips IC1 to protect them. To support theliquid crystal display element PNL, however, it is necessary to providea rubber spacer in a wide area, making it impossible to narrow thepicture-frame area of the liquid crystal display module MDL.

FIG. 49F represents a case where the vinyl chloride spacer CLSPC isprovided between the drain driver chips IC1 and on a connecting portionwhere the liquid crystal display element PNL and the video signalline-side flexible printed circuit board FPC2 are stacked together. Inthe example of FIG. 49F, the space where the IC1s are mounted is securedby the vinyl chloride spacer CLSPC as shown in FIG. 49D and because theCLSPC covers up to the connecting portion of the FPC2 and the PNL, thestresses which the CLSPC imparts to the SUB1 can be distributed,preventing the IC1 and the SUB1 from being broken even when subjected toimpacts of 100G or more. In the example of FIG. 49F, because the CLSPCsupports the connecting portion of the PFC2 and the PNL, the reliabilityof the connecting portion improves.

While the above description of the case of the drain driver chip IC1 hasbeen made, the same can apply to the gate driver chip IC2.

The other constructions not described in the above are similar to thoseof the first embodiment.

Embodiment 6

Narrowing the picture-frame area of the liquid crystal display moduleMDL gives rise to a problem in that the liquid crystal display elementPNL, when subjected to strong impacts, may be displaced from itsposition in the liquid crystal display module MDL. It is thus necessaryto firmly fix the PNL to the shield case SHD.

FIG. 50A and FIG. 50B show one example in which the glass substratesSUB1, SUB2 of the liquid crystal display element PNL are fixed to theshield case SHD. In the example of FIG. 50A and FIG. 50B, the PNL isbonded to the SHD with a double-sided adhesive tape BAT along threesides of the PNL on the drain driver chip IC1 side (D side), the gatedriver chip IC2 side (G side) and the liquid crystal injection portside. By securing the three sides of the PNL to the SHD with the BAT,the position of the PNL does not change relative to the SHD even when itis subjected to impacts. Further, by securing four sides of the PNL tothe SHD with a BAT, the PNL does not shift in position with respect tothe SHD even when subjected to impacts greater than 220G.

Although the PNL may be bonded to the backlight, or more specificallythe frame spacer WSPC, to protect the PNL against damage due to impacts,there is a possibility of the side surface of the PNL being shifted.

FIGS. 51A and 51B represent an example in which the glass substratesSUB1, SUB2 of the liquid crystal display element PNL are secured to theshield case SHD. Because it incorporates measures against breakage ofthe glass substrates and the breakage of the drain driver chip describedin Embodiment 3 and Embodiment 5, the embodiment of FIG. 51A and FIG.51B has greater strength than the embodiment shown in FIG. 50A and FIG.50B. In the embodiment of FIG. 51A and FIG. 51B the PNL is secured tothe SHD with a double-sided adhesive tape BAT at three sides except forthe D side and thus the position of the PNL can be kept from beingshifted relative to the SHD. Further, as shown in FIG. 51B, the opposingsubstrate SUB2 is bonded to the SHD with a BAT on the G side to preventthe SHD from butting against and breaking the gate driver chip IC2.

The other constructions of this embodiment not described above are thesame as those of the first embodiment.

As described above, this invention can reduce the picture-frame area ofthe liquid crystal display device not contributing to the image displayand realize a liquid crystal display device which is compact but has alarge display screen.

What is claimed is:
 1. A liquid crystal display device comprising: aliquid crystal display element; a backlight for supplying light to theliquid crystal display element and including a light guide plate, afluorescent tube arranged at a side of the light guide plate, and a lampreflector arranged along the fluorescent tube; a resin mold caseaccommodating the light guide plate, the fluorescent lamp, and the lampreflector and having an opening; and a metal case having a upper framemember and a lower shielding member, and accommodating the backlightaccommodated in the resin mold case and the liquid crystal displayelement arranged over the resin mold case to be opposite to an uppersurface of the light guide plate through the opening therein; whereinsaid backlight further includes bushings formed of an insulatingmaterial, and a lamp cable extending along said fluorescent tube, saidlamp reflector holding said fluorescent tube through said bushings, saidlamp cable being connected to one end of said fluorescent tube andinterposed between said lamp reflector and said resin mold case, andsaid lamp reflector being a bent metal plate having a slit in which saidlamp cable is inserted.
 2. A liquid crystal display device according toclaim 1, wherein said metal plate of said lamp reflector is brass.
 3. Aliquid crystal display device according to claim 1, wherein said metalplate of said lamp reflector is aluminum.
 4. A liquid crystal displaydevice according to claim 1, wherein silver is deposited on a surface ofsaid lamp reflector.
 5. A liquid crystal display device according toclaim 1, wherein a light reflection surface of said lamp reflector is aprocessed surface for increasing light reflectance.
 6. A liquid crystaldisplay device according to claim 1, wherein said bushings are made ofelastic material.
 7. A liquid crystal display device according to claim1, wherein said bushings are made of rubber.
 8. A liquid crystal displaydevice according to claim 1, wherein said slit is formed at a portion ofsaid lamp reflector holding one of said bushings in which said one endof said fluorescent lamp is connected to said lamp cable.
 9. A liquidcrystal display device according to claim 1, wherein one of saidbushings in which said one end of said fluorescent lamp is connected tosaid lamp cable has a protrusion protruded along said side of said lightguide plate.
 10. A liquid crystal display device according to claim 9,wherein said protrusion of said one of said bushings is inserted intosaid lamp reflector.
 11. A liquid crystal display device according toclaim 1, wherein a voltage applied to said one end of said fluorescentlamp is lower than a voltage applied to another end of said fluorescenttube.
 12. A liquid crystal display device comprising: a liquid crystaldisplay element; a backlight including a light guide plate having anupper surface arranged opposite to the liquid crystal display element, afluorescent tube arranged at a side of the light guide plate, a lampreflector arranged along the fluorescent tube, and a lamp cableconnected to one end of the fluorescent tube and extended along thefluorescent tube; a resin case accommodating the light guide plate, thefluorescent lamp, the lamp reflector, and the lamp cable, and includingof a resin frame member arranged at an upper surface side of the lightguide plate and a resin mold member arranged at a lower surface side ofthe light guide plate; and a metal case accommodating the resin case andthe liquid crystal display element which is arranged over the resincase, the metal case including a metal frame member and a metalshielding member.
 13. A liquid crystal display device according to claim12, wherein the resin frame member is disposed at a main surface side ofthe light guide plate opposite to the liquid crystal display element andthe resin mold member is disposed at another main surface side thereof.14. A liquid crystal display device according to claim 13, wherein theresin frame member is colored black.
 15. A liquid crystal display deviceaccording to claim 13, wherein a diffusion sheet and a prism sheet areinterposed between the resin frame member and the light guide plate. 16.A liquid crystal display device according to claim 13, wherein areflection sheet is interposed between the resin mold member and thelight guide plate.
 17. A liquid crystal display device according toclaim 12, wherein the resin frame member and the resin mold member arefixed to one another at a periphery of the light guide plate.
 18. Aliquid crystal display device according to claim 12, wherein the lampreflector is formed of a metal plate being bent so that one surface ofthe metal plate surrounds the fluorescent tube, and the lamp cable isheld between another surface of the metal plate and the resin case. 19.A liquid crystal display device according to claim 18, wherein the lampreflector has a hollowed portion in the another surface of the metalplate along the fluorescent tube, and the hollowed portion is formed bybending the metal plate toward the fluorescent tube to provide aprotrusion in the one surface of the metal plate.
 20. A liquid crystaldisplay device according to claim 12, wherein a voltage applied to theone end of the fluorescent lamp is lower than a voltage applied toanother end of the fluorescent tube.
 21. A liquid crystal display deviceaccording to claim 12, wherein the liquid crystal display element has athin film transistor in each of a plurality of pixels formed therein,and the fluorescent lamp and the lamp reflector is arranged at a side ofthe liquid crystal display element at which drain driver circuitssupplying video signals to the thin film transistors are arranged.
 22. Aliquid crystal display device according to claim 12, wherein the metalframe member is disposed over a periphery of the liquid crystal displayelement, and the metal shielding member is disposed under the resin moldmember.
 23. A liquid crystal display device according to claim 12,wherein the lamp cable is held between the resin case and the lampreflector formed of a metal plate.